It has been recognized that in principle the lower unsaturated hydrocarbon component in certain hydrocarbon streams is a valuable source for higher organic molecules. Such higher organic molecules may be reached, for example, by treatment, for example hydroformylation, of unsaturated hydrocarbons, in particular those containing two carbon atoms, the unsaturated hydrocarbons being obtainable, for example, by pyrolysis of hydrocarbons, more especially their pyrolysis in the presence of steam to form a light olefin-containing mixture, or pyrolysis of methane in appropriate conditions, as described in U.S. patent application Ser. No. 375,324 of Jan. 18th, 1995, and a corresponding PCT application entitled "Direct Hydroformylation of a Multi-Component Synthesis Gas Containing Carbon Monoxide, Hydrogen, Ethylene and Acetylene", applicants Gabor Kiss et al., assigned to Exxon Research & Engineering Company, filed simultaneously with the present application, and whose entire disclosures are incorporated by reference herein.